The only caveat is that:
1. We do not properly recognize when we have a let binding and we
perform a guaranteed dynamic call. In such a case, we add an extra
retain, release pair around the call. In order to get that case I will
need to refactor some code in Callee. I want to make this change, but
not at the expense of getting the rest of this work in.
2. Some of the protocol witness thunks generated have unnecessary
retains or releases in a similar manner.
But this is a good first step.
I am going to send a large follow up email with all of the relevant results, so
I can let the bots chew on this a little bit.
rdar://19933044
Swift SVN r27241
Consistently open all references into existentials into
opened-existential archetypes within the constraint solver. Then,
during constraint application, use OpenExistentialExprs to record in
the AST where an existential is opened into an archetype, then use
that archetype throughout the subexpression. This simplifies the
overall representation, since we don't end up with a mix of operations
on existentials and operations on archetypes; it's all archetypes,
which tend to have better support down the line in SILGen already.
Start simplifying the code in SILGen by taking away the existential
paths that are no longer needed. I suspect there are more
simplifications to be had here.
The rules for placing OpenExistentialExprs are still a bit ad hoc;
this will get cleaned up later so that we can centralize that
information. Indeed, the one regression in the compiler-crasher suite
is because we're not closing out an open existential along an error
path.
Swift SVN r27230
These aren't really orthogonal concerns--you'll never have a @thick @cc(objc_method), or an @objc_block @cc(witness_method)--and we have gross decision trees all over the codebase that try to hopscotch between the subset of combinations that make sense. Stop the madness by eliminating AbstractCC and folding its states into SILFunctionTypeRepresentation. This cleans up a ton of code across the compiler.
I couldn't quite eliminate AbstractCC's information from AST function types, since SIL type lowering transiently created AnyFunctionTypes with AbstractCCs set, even though these never occur at the source level. To accommodate type lowering, allow AnyFunctionType::ExtInfo to carry a SILFunctionTypeRepresentation, and arrange for the overlapping representations to share raw values.
In order to avoid disturbing test output, AST and SILFunctionTypes are still printed and parsed using the existing @thin/@thick/@objc_block and @cc() attributes, which is kind of gross, but lets me stage in the real source-breaking change separately.
Swift SVN r27095
The set of attributes that make sense at the AST level is increasingly divergent from those at the SIL level, so it doesn't really make sense for these to be the same. It'll also help prevent us from accidental unwanted propagation of attributes from the AST to SIL, which has caused bugs in the past. For staging purposes, start off with SILFunctionType's versions exactly the same as the FunctionType versions, which necessitates some ugly glue code but minimizes the potential disruption.
Swift SVN r27022
Previously some parts of the compiler referred to them as "fields",
and most referred to them as "elements". Use the more generic 'elements'
nomenclature because that's what we refer to other things in the compiler
(e.g. the elements of a bracestmt).
At the same time, make the API better by providing "getElement" consistently
and using it, instead of getElements()[i].
NFC.
Swift SVN r26894
The condition we want is that the operand type has reference semantics (or is an Optional of a reference type), not necessarily that it is a single retainable pointer. The latter disallows class existentials and functions from being unowned. Fixes rdar://problem/20374500.
Swift SVN r26883
threaded into IRGen; tests to follow when that's done.
I made a preliminary effort to make the inliner do the
right thing with try_apply, but otherwise tried to avoid
touching the optimizer any more than was required by the
removal of ApplyInstBase.
Swift SVN r26747
The witness calling convention is for dispatching via the witness
table, which is not the case for protocol extensions. At some point,
it might make sense for protocol extensions to use the witness calling
convention, but for now the native method calling convention
suffices.
Swift SVN r26616
Remove the semantic restrictions that prohibited extensions of
protocol types, and start making some systematic changes so that
protocol extensions start to make sense:
- Replace a lot of occurrences of isa<ProtocolDecl> and
dyn_cast<ProtocolDecl> on DeclContexts to use the new
DeclContext::isProtocolOrProtocolExtensionContext(), where we want
that behavior to apply equally to protocols and protocol extensions.
- Eliminate ProtocolDecl::getSelf() in favor of
DeclContext::getProtocolSelf(), which produces the appropriate
generic type parameter for the 'Self' of a protocol or protocol
extension. Update all of the callers of ProtocolDecl::getSelf()
appropriately.
- Update extension validation to appropriately form generic
parameter lists for protocol extensions.
- Methods in protocol extensions always use the witnesscc calling
convention.
At this point, we can type check and SILGen very basic definitions of
protocol extensions with methods that can call protocol requirements,
generic free functions, and other methods within the same protocol
extension.
Regresses four compiler crashers but improves three compiler
crashers... we'll call that "progress"; the four regressions all hit
the same assertion in the constraint system that will likely be
addressed as protocol extensions starts working.
Swift SVN r26579
This allows types to be lowered as scalar reference-counted types without requiring them to have AST-level reference semantics. For now, put in a staging assertion to ensure isReferenceCounted == hasReferenceSemantics to make sure we set the bit properly everywhere.
Swift SVN r26238
TerminatorInsts. Now you can walk over the successor list of a terminator
and actually modify the SILSuccessor directly, allowing better CFG
transformations. NFC.
Swift SVN r26140
sil-verifier was using SIL types to check metatypes. But metatypes, especially metatypes of metatypes, use AST types. Therefore checks should be done based on AST types.
rdar://20153162
Swift SVN r26111
We discussed it with Joe and this requirement does not make sense, especially if casts are produced by one pass, but optimized by another one. Moreover, having equal from and to types is eventually not very efficient, but is not semantically wrong. Such casts can often be produced by the inliner or specialised.
Swift SVN r26110
Give SILType 'getPreferredExistentialRepresentation' and 'canUseExistentialRepresentation' methods, which track what types of container particular existential types may use--fixed-sized, class-constrained, metatype, or box. Allow for existentials to use a specialized representation for certain known concrete types by allowing these methods to take a concrete type. NFC yet, except to replace some ad-hoc verifier conditions with canUseExistentialRepresentation checks where appropriate.
Swift SVN r26062
This can only happen in the closure specializer and the generic
specializer since all other specializations either copy the linkage of
the original function (function signature opts) or clone closures/thunks
which have shared linkage.
I put in a verifier check that makes sure we do not create shared
versions of these functions. The real problem has to do with serializing
these sorts of functions, but since we always serialize shared
functions, it makes sense to just ban it.
rdar://20082696
Swift SVN r26001
This is useful for cleaning-up the code generated by intermediate transformations, e.g. for cases where we perform folding of always failing casts into traps followed by an unreachable instruction. I'll make use of it in my subsequence commits.
Swift SVN r25988
For better consistency with other address-only instruction variants, and to open the door to new exciting existential representations (such as a refcounted boxed representation for ErrorType).
Swift SVN r25902
When we clone loops with exit blocks that are unreachable the verifier
complained before this patch.
loop:
= alloc_stack
cond_br %overflow_cond, loop_latch, unreachable_only_exit
loop_latch:
cond_br loop, exit
unreachable_only_exit:
..
unreachable
We don't care about stack deallocation on paths that must lead to
unreachable.
The alternative to weaken the verifier for cases like this would be to clone
loop exits that are guaranteed to lead to unreachable which would be a waste of
space.
Swift SVN r25732
This makes it easy to find no-return functions since one must iterate
through all BB with unreachable terminators and check the previous
instruction.
Swift SVN r25004
the call instead of during the formal evaluation of the argument.
This is the last major chunk of the semantic changes proposed
in the accessors document. It has two purposes, both related
to the fact that it shortens the duration of the formal access.
First, the change isolates later evaluations (as long as they
precede the call) from the formal access, preventing them from
spuriously seeing unspecified behavior. For example::
foo(&array[0], bar(array))
Here the value passed to bar is a proper copy of 'array',
and if bar() decides to stash it aside, any modifications
to 'array[0]' made by foo() will not spontaneously appear
in the copy. (In contrast, if something caused a copy of
'array' during foo()'s execution, that copy would violate
our formal access rules and would therefore be allowed to
have an arbitrary value at index 0.)
Second, when a mutating access uses a pinning addressor, the
change limits the amount of arbitrary code that falls between
the pin and unpin. For example::
array[0] += countNodes(subtree)
Previously, we would begin the access to array[0] before the
call to countNodes(). To eliminate the pin and unpin, the
optimizer would have needed to prove that countNodes didn't
access the same array. With this change, the call is evaluated
first, and the access instead begins immediately before the call
to +=. Since that operator is easily inlined, it becomes
straightforward to eliminate the pin/unpin.
A number of other changes got bundled up with this in ways that
are hard to tease apart. In particular:
- RValueSource is now ArgumentSource and can now store LValues.
- It is now illegal to use emitRValue to emit an l-value.
- Call argument emission is now smart enough to emit tuple
shuffles itself, applying abstraction patterns in reverse
through the shuffle. It also evaluates varargs elements
directly into the array.
- AllowPlusZero has been split in two. AllowImmediatePlusZero
is useful when you are going to immediately consume the value;
this is good enough to avoid copies/retains when reading a 'var'.
AllowGuaranteedPlusZero is useful when you need a stronger
guarantee, e.g. when arbitrary code might intervene between
evaluation and use; it's still good enough to avoid copies
from a 'let'. The upshot is that we're now a lot smarter
about generally avoiding retains on lets, but we've also
gotten properly paranoid about calling non-mutating methods
on vars.
(Note that you can't necessarily avoid a copy when passing
something in a var to an @in_guaranteed parameter! You
first have to prove that nothing can assign to the var during
the call. That should be easy as long as the var hasn't
escaped, but that does need to be proven first, so we can't
do it in SILGen.)
Swift SVN r24709
If a subclass overrides methods with variance in the optionality of non-class-type members, emit a thunk to handle wrapping more optional parameters or results and force-unwrapping any IUO parameters made non-optional in the derived. For this to be useful, we need IRGen to finally pay attention to SILVTables, but this is a step on the way to fixing rdar://problem/19321484.
Swift SVN r24705
This exposes a problem with the sil_vtable parser, that it can't differentiate overloads (rdar://problem/19572342), and breaks a test that exposes the fact we don't reabstract overrides that have a less abstract native calling convention than their base (rdar://problem/19572664).
Swift SVN r24667
Write up a requireABICompatibleFunctionTypes check to make sure two function types share the same ABI. The real target here is to be able to apply this to vtable entries in order to uncover variance bugs like rdar://problem/19321484, but convert_function is a convenient testbed.
Swift SVN r24666
obviously broken cases (when an alloc stack has its dealloc_stack in the same block
as the allocation, it checks that there are no uses in other blocks) but this isn't
correct: uses in dead blocks are fine. Just ignore them.
Swift SVN r24357
Rather than dropping generics on the cloned capture, retain them and
create the new partial apply with substitutions.
Thanks to Erik for some initial debugging, the verifier improvement, and
a small test case to start with!
Swift SVN r24024
storage for arbitrary values.
A buffer doesn't provide any way to identify the type of
value it stores, and so it cannot be copied, moved, or
destroyed independently; thus it's not available as a
first-class type in Swift, which is why I've labelled
it Unsafe. But it does allow an efficient means of
opaquely preserving information between two cooperating
functions. This will be useful for the adjustments I
need to make to materializeForSet to support safe
addressors.
I considered making this a SIL type category instead,
like $@value_buffer T. This is an attractive idea because
it's generally better-typed. The disadvantages are that:
- it would need its own address_to_pointer equivalents and
- alloc_stack doesn't know what type will be stored in
any particular buffer, so there still needs to be
something opaque.
This representation is a bit gross, but it'll do.
Swift SVN r23903
It avoids generation of llvm phi nodes with identical predecessors and differing values.
This change replaces my previous fix of this problem in r23580, where I handled it in IRGen.
There were some discussions about it with the conclusion that it's better to just disallow such cond_br instructions in SIL.
It makes the life easier for some SIL optimizations which can't deal with cond_br with identical destinations.
The original radar is <rdar://problem/18568272> Swift compiler fails with "PHI node has multiple entries for the same basic block with different incoming values!"
Swift SVN r23861
Verify that witness_method instructions with a lookup type that is an
opened archetype have the optional operand that represents the
open_existential instruction.
I ran into this working supporting substitution of existential types in
mandatory inlining (rdar://problem/17769717).
Swift SVN r23665
